Geoff Wood is still around (he collected the Lish Young By A Broom) and ,in fact, still performing most weeks at his regular club the Grove in Leeds on a friday. He seems to have taken to reciting poems by people like W.B Yeats - but does them from memory, which is quite impressive.I'll ask him when I see him in a week or two - but I always assumed "lish" was simply a condensation of "delicious".
... and for your delectation and delight here are two more songs almost always attributed wrongly as irish - The Black Velvet Band (from Harry Cox) and The Wild Rover (from loads of english singers)